It is applicable more particularly for collimating beams of neutrons and beams of X rays.
Frequently, it may be desired to limit the angular distribution of a radiation beam without actually losing its luminosity.
In order to achieve this, a Soller collimator is used.
An example of this type of collimator is diagrammatically shown on FIG. 1.
It includes a plurality of fine parallel thin strips 2 which are able to absorb the incident radiation 4 it is desired to collimate, or strips which are coated with a material able to absorb this radiation.
The ratio Do/Lo of the distance between the strips 2 to the length Lo of these strips is equal to the tangent of half the desired maximum divergence 2.phi. for the radiation beam 6 coming out of the collimator.
So as to avoid wasteful losses, the finest thin strips are used.
A Soller collimator does, however, have drawbacks.
In fact, if the radiation to be collimated arrives below a certain critical angle of incidence on the thin strips, it is reflected (total reflection effect), despite the presence of the absorbing material.
Accordingly, it is not possible to collimate the incident radiation beam below the critical angle.
In addition, this total reflection risks contaminating (this not being desired) the radiation beam diffused by a sample (not shown on FIG. 1) which is illuminated by the collimated beam.